In the fields of orthodontics and prosthodontics, different methods are known to determine a current teeth topology in a patient's mouth. One of the methods involves taking an impression of a patient's dentition. Using this impression, a plaster cast is made, representing a (positive) physical teeth model. This physical teeth model may then be used for a subsequent treatment plan.
If CAD (computer-aided design) and/or CAM (computer-aided manufacturing) techniques are to be employed, a digital dataset corresponding to the teeth may be obtained by scanning. For example, the (positive) physical teeth model in form of the plaster cast or a (negative) physical teeth model in form of the impression may be scanned or imaged using x-rays, computed tomography, magnetic resonance imaging, or laser scanning apparatuses. With the thus obtained image data, a computer model of the teeth or a part thereof may be established. However, such methods and apparatus can be somewhat time consuming and more expensive than would be ideal.
As an alternative, teeth in a patient's mouth may be imaged directly. For this purpose, different imaging apparatuses are known.
The prior apparatus for non-contact imaging with a probe having a sensing face have been less than ideal in at least some respects. The prior probe devices can be somewhat larger than would be ideal, and may have a large intraoral front tip which can make the prior devices somewhat cumbersome to use in at least some instances. Although an array of incident light beams passing through focusing optics can be used, the larger than ideal probe heads of such devices can provide less than ideal measurements of the oral cavity of a patient. Also, the prior devices that rely on beams to generate illuminated spots on the structure and the intensity of returning light rays propagating along an optical path can be somewhat cumbersome to use and maintain and can be somewhat more costly to manufacture than would be ideal.
Although quarter wave plates (QWPs) have been used with prior devices, the prior QWPs can provide less than ideal results in at least some instances. For example, disposable QWPs can have less than ideal quality and can be less available than would be ideal. Although fixed QWPs have been proposed, the alignment and reliability of fixed QWPs can be less than ideal. Also, the use of QWPs can be associated with less than ideal numerical apertures and accuracy, and may be less than ideally suited for combination with telecentric measurement systems. Also, the use of QWPs can provide an additional optical component that can be related to less than ideal control of contamination, for example.
Although three dimensional (3D) data acquisition using triangulation has been proposed, such devices can be less compact than would be ideal and can be somewhat difficult to place in the mouth of the patient. Also, such devices can require alignment and can be less accurate and reliable than would be ideal in at least some instances.
In light of the above, improved methods and apparatus for measuring surfaces such as the intraoral cavity are needed. Ideally such methods and apparatus will overcome at least some of the deficiencies of the prior methods and apparatus and be more accurate, reliable, compact, easier to use with the patient's mouth and less costly than the prior devices.